Apparatus for manufacturing box springs

ABSTRACT

An apparatus for assembling box spring &#39;&#39;&#39;&#39;constructions&#39;&#39;&#39;&#39; by stapling rows of springs to a base frame. The apparatus utilizes a wire spring coil in which the wire at one end of the coil is bent to cross the bottom convolution so that a stapling gun inserted axially into the spring from the other end will secure the spring to the frame with one staple. The staple is driven with enough force to impress the cross-wire into the surface of the frame. The apparatus handles the springs and frames upside down, the guns being lowered for loading with springs, and raised for firing. The gun muzzles are adapted to receive an inverted spring and to position it rotatively so that the staple when driven will encircle the cross-wire from which the spring is suspended on the gun. After each firing, the frame indexes for another row, and is followed at a controlled interval by a second frame brought into the mechanism automatically from a magazine.

United States Patent [1 1 Stumpi 1 Nov. 6, 1973 1 APPARATUS FOR MANUFACTURING BOX SPRINGS [75] Inventor: Walter Stumpf, Munster, Ind.

[73] Assignee: Simmons Company, New York, N.Y.

[22] Filed: Jan. 18, 1972 [21] Appl. No; 218,843

Related U.S. Application Data [62] Division of Ser. No. 829,533, June 2, 1969,

abandoned.

[52] US. Cl. 227/48, 227/39 [51] llnt. Cl 1327f 7/14 [58] Field of Search 227/7, 39, 48, 50,

[56] References Cited UNITED STATES PATENTS 3,084,345 4/1963 Hodges, Jr. 227/48 X 3,168,745 2/1965 Winters 227/39 3,261,527 7/1966 Steiner 227/7 Primary Examiner-Granville Y. Custer, Jr. AttorneyAnderson, Luedeka, Fitch, Even & Tabin [57] ABSTRACT An apparatus for assembling box spring constructions by stapling rows of springs to a base frame. The apparatus utilizes a wire spring coil in which the wire at one end of the coil is bent to cross the bottom convolution so that a stapling gun inserted axially into the spring from the other end will secure the spring to the frame with one staple. The staple is driven with enough force to impress the cross-wire into the surface of the frame.

The apparatus handles the springs and frames upside down, the guns being lowered for loading with springs, and raised for firing. The gun muzzles are adapted to receive an inverted spring and to position it rotatively so that the staple when driven will encircle the cross-wire from which the spring is suspended on the gun.

After each firing, the frame indexes for another row, and is followed at a controlled interval by a second frame brought into the mechanism automatically from a magazine.

7 Claims, 13 Drawing Figures PATENTED NOV 6 I973 SHEET 10F 7 FlG.l

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PATENTED NOV 6 I975 SHEET 7 BF 7 ouus UP BACKING BAR oovm TRIGGER BAR mm: moex IIIM |1.|.L

ZOZHtmmO 449242 |sa T suus UP media as FRAME No "max FRAME-STOP RESET BACKING BAR DOWN APPARATUS FOR MANUFACTURTNG BOX SPRINGS This is a division of my copending application, Ser. No. 829,533, filed June 2, 1969 and now abandoned.

This invention relates to the manufacture of box springs, by which term I mean to include not only box springs as such, i.e., upholstered spring constructions mounted upon flat wooden frames and usually employed upon a bedstead or bedframe as a foundation for a mattress, but also similar such upholstered constructions employed as bases of studio couches, upholstered sofas, upholstered chairs, and the like.

The invention relates particualarly (1) to a method of assembling springs into a construction, i.e., the arrangement of individual coil springs into a series of rows in regular pattern by virtue of the attachment of such spring coils individually to a base frame of wood or the like by means of stapling; (2) to a special apparatus for carrying out the method; and (3) to a particular form of spring coil which is particularly adapted to the practice of the method.

Since the days of the hand-tied box-spring construction, which once constituted a majority of those made, particularly those of higher quality, various attempts have been made to adapt the box spring for machine assembly without a great deal of success. Until recently, machine assembly of box springs has been limited to the use of pre-assembled Spring constructions of hour-glass coils such as are used in mattresses, i.e., adjacent rows of springs united by helical tie-wires, and the stapling of such assemblies or spring constructions as a unit to a wooden slat frame. This technique is essentially limited to the double-cone or hour-glass type of coil, which has limitations both functional and economic when used as a box spring, particularly for certain kinds of mattresses that best serve their function when emplaced upon a relatively inflexible but resiliently mounted platform.

Assembly of box spring constructions of the conecoil type, which is preferred for many sleeping and sitting cushion-bases, has been performed essentially by hand, the spring coils being assembled by hand methods into an assembly or construction of sutiable size, which is then secured to a wooden slat frame by stapling. The process remains expensive because of the labor involved, and unless considerable care be taken, the construction can be noisy if the contacting metallic parts are not tightly interlocked.

While some attempts have heretofore been made to simplify the assembly of box springs by stapling cone coils individually to the wooden base frame, the methods employed have been cumbersome and incapable of realizing the full potential of the stapling technique because they have contemplated the use of the conventional coil, and have accepted all of its limitations as premises.

It is the primary object of this invention, therefore, to improve the mechanized manufacture of box springs, this object being accomplished by a change in the character of the cone coil, the provision of a stapling gun and technique adapted to handle such a coil and to secure it to the slat frame with a single staple, and the provision of the necessary apparatus to bring the component parts together in a coordinated assembly, each of these aspects being believed novel as defined by the claims herein.

SUMMARY STATEMENT The apparatus of this invention utilizes the stapling technique to fuller advantage by coupling it with a specially designed cone coil so that each coil is securely anchored and positioned by a single staple.

For the purposes of the technique and the apparatus hereinafter described, this special form of coil may be differentiated from others now in common use in that, at its small end, the final convolution terminates in a chordal element which extends across the end convolution approximately diametrically thereof. This chordal element or cross bar at the small end of the coil becomes not only the means for positioning and anchoring the coil on the wooden slat frame, but is also the means by which the coil is supported in the assembly apparatus, as well as the reference for orienting the spring coils rotatively so as to position properly the knots at their large ends for later assembly of the supporting face of the box spring construction.

To summarize the assembly technique as briefly as possible, the above-described coil is placed over the nose of a stapling gun, the muzzle of which has been modified to receive the aforementioned cross bar at the small end of the cone coil in such manner that the staple when driven will encircle that bar approximately midway thereof. In order to eliminate extraneous holding means for maintaining this relationship of spring coil and stapling gun for the stapling operation, the stapling is preferably performed with the stapling gun pointed upwardly so that gravity holds the coil in place. The obvious corollary is that the flat frame of the box spring is inverted and overhead, the assembly being made in the upside-down condition, the stapling gun with coil thereon being moved vertically upwardly with respect to the slat frame to position the coil thereon for stapling. The gun is then fired with sufficient force not only to drive the staple securely into the wood and into encircling engagement with the cross bar of the spring, but also to impress or to indent the cross bar itself firmly into the wood.

The apparatus includes the vertically positioned upwardly directed stapling guns in ganged or banked array suitable for stapling at least one row of springs at a time to the base frame. The guns are mounted on a movable carriage which is moved by power from a lower loading position to an upper firing position, and the stapling guns are suitably powered from a common source and fired simultaneously by a common trigger control. The inverted slat frame moves in suitable overhead ways, and is bucked by a suitable backing arrangement at the stapling station, to which and from which each cross slat of the base frame is indexed in turn toreceive a row of coils.

These successive operations are organized into a selfterminating cycle by means of a suitable programming controller such that the operator, after having charged each operative gun with a spring coil, manually initiates the cycle which is thereafter self-executing, and at the end of which the guns are returned to the loading station, ready to be charged with another row of coils for the commencement of yet another cycle.

While I have found it desirable from the standpoint of simple explanation of the several steps of the method and features of the apparatus to speak of hand loading the coils on the guns, I also contemplate the charging of the guns by machine as well, using a feeding apparatus of the kind disclosed in my U.S. Pat. No. 3,193,136 for presenting the inverted spring coils one at a time from a nested stack of the same, to be picked up by the stapling gun passing axially upwardly through the spring coil at such feeding station.

THE DRAWINGS The invention is described in detail in connection with the accompanying drawings in which:

FIG. 1 is a fragmentary perspective view of a box" spring construction partially completed in accordance with the invention, showing the spring assembly at one corner of the box spring frame;

FIG. 2 is a side elevational view of the basic elements of the assembly apparatus, illustrating the sequence of operations by means of which the spring coil is carried by the stapling gun upwardly to the slat frame and stapled thereto;

FIG. 3 is a side elevational view of the overall apparatus showing a supply stack or magazine of the slat frames on the right, uppermost one of which is on the ways and in the position at which its leading cross slat awaits a row of springs at the stapling station at the far left;

FIG. 4a is an elevational view of the stapling mechanism as the operator sees it, i.e., from the right-hand side of the mechanism as seen in FIG. 3, FIG. 4a showing the guns in retracted position and charged with spring coils sufficient for a box spring of less-thanfull width, and showing the overhead ways moved inwardly to accommodate the less-than-full-width slat frame;

FIG. 4b is a similar but fragmentary elevational view of the mechanism shown in FIG. 4a, but showing the guns ready for firing, i.e., with the spring coils elevated into contact with the cross slat of the wood frame, and the overhead backing bars cammed into solid bucking or shock-receiving contact with the upper side of the slat;

FIG. 5 is a fragmentary perspective view of the stapling mechanism as seen from the operators station, showing in greater detail the gun and its mounting, and the elevating and triggering mechanisms;

FIG. 6a, FIG. 6b, and FIG. 60 are each enlarged, fragmentary sectional elevational views of the frame feeding or indexing mechanism, shown in the upper lefthand portion of FIG. 3, for positioning each successive cross slat of the box frame at the stapling station, FIG. 6a showing the end or leading cross slat positioned to receive its coils, FIG. 6b showing the slat frame in transit as the second cross slat of the frame is moved into the stapling station, and FIG. 6c illustrating the second cross slat at the stapling station, and illustrating as well how each succeeding cross slat of the frame is thereafter so positioned;

FIG. 7 is an enlarged fragmentary end elevational view of the indexing mechanism seen from the exiting end of the apparatus, i.e., the left hand end as illustrated in FIG. 3;

FIG. 8a is an enlarged fragmentary elevational view of a portion of the indexing mechanism, showing in particular the mechanism for ejecting a completed assembl FIG. Sb is an enlarged fragmentary view of the indexing apparatus showing the controller for the frame ejector of FIG. 8a; and

FIG. 9 is a diagram of the electrical circuit and controller by means of which the aforementioned individual operations are coordinated in an operating cycle.

THE SPRING COIL PROPER The spring coil 20 is best seen in FIG. 1. It is a somewhat modified cone coil in that its five and one-half convolutions do not decrease in diameter linearly but rather abruptly from the major diameter of the upper knotted convolution 22 to the main body of the coil, which is of substantially smaller and so nearly uniform diameter as to be almost cylindrical in appearance as compared with the usual cone coil. To those familiar with the spring art, it is apparent that this kind of coil exhibits a fairly abrupt change in load carry from an initial softness to a considerable stiffness as the first or closed convolution deflects sufficiently to bring the succeeding convolution of smaller diameter into contact with the load to be supported.

At its unknotted bottom end 24, the wire of the spring coil terminates in a chordal element or cross liar 26 which is approximately the length of the minor diameter of the coil and is positioned approximately diametrically of the bottom convolution. This chordal cross bar serves a number of purposes, not only in the construction of the box spring itself but also in the handling and the orientation of the coil by the assembly apparatus.

As will be seen in FIG. 1, the cross bar 26 at the bottom of the coil is at or near the central axis of the coil, and also lies in the plane that intercepts the knot 23 at the top convolution. Inasmuchas the location of the knot at the top of the coil can be important to the particular one of many available methods for joining the individual coils together at their upper ends, the desired final position of the knot 28 may easily be derived from the bottom cross bar 26 as a reference, inasmuch as the muzzle of the stapling gun, as will hereinafter be pointed out in detail, is adapted to receive the spring coil in only one of two alternate positions displaced degrees from one another.

Therefore, when the spring coil, as is indicated in FIG. 1, is made so that the cross bar 26 and the knot 28 share a common plane with the central axis of the coil, and when, as later will be described, the muzzles of the guns are arranged to receive the cross bars of the coils to position them only crosswise of the cross slat 30 of the slat frame 32, it is apparent that the position of the knot 28 at the upper end of the coil must be either on one side or the other of the cross slat 30 or, stated with reference to the direction of movement of the slat frame 32 through the apparatus, must either be fore or aft, i.e., on the leading or trailing edge of the spring.

I have found such orientation preferable to a number of kinds of top face assembly of the box-spring construction, and as a matter of practice, all of the springs of all but the last row are usually positioned with their knots trailing with respect to the direction of advancement through the assembly machine, the knots of the last row of springs being presented with knots leading, so that each of the peripheral springs presents a smooth unknotted edge of the top convolution for tangential connection to an encircling border wire or frame (not shown).

It is equally conceivable, however, that for some form of top-face assembly of the construction, an orientation of the spring coil to position its knots other than precisely leading or precisely trailing may be preferred, in which event some other relative rotative dis placement of the cross bar 26 at the bottom end of the coil and the knot 28 at the upper end of the coil may be preferred. In any case, however, the chordal cross bar 26 at the bottom of the coil serves as the reference from which the coil is positioned.

As will be noted from FIGS. 1 and 2, as well as other views, the slat frame 32 comprises the leading end slat 30, narrower intermediate cross slats 3i, and a trailing end slat 33 (FIG. 8b only). These are nailed to longitudinal side rails 34, the ends slats and 33 each having a second layer 30a and 33a in a common plane with the side rails 34. In frames of greater width than the twinsize frame shown, a center rail would also be provided.

The individual stapling guns 35 ganged for unison operation in the assembly apparatus (FIGS. 4a and 4b), are powered by air, as is conventional with commercial industrial staplers, and are arranged, as will be apparent from FIG. 4a, in a line abreast upon a vertically reciprocable carriage 36 which itself is powered to travel between a retracted, lower, coil-loading position, shown in FIG. 4a, and an upper or firing position, illustrated in FIG. 417. A particualrly unique feature of the gun itself is that its muzzle is equipped with a surrounding sleeve 38 which is preferably of a slippery material such as Nylon, Teflon, or the like, is generally cylindrical in shape and of a diameter slightly less than the minor diameter of the cone coil, and is chamfered or cone shaped at its upper end to facilitate the emplacement of the inverted cone coil thereupon.

The small upper end of the sleeve 38 is provided with a diametrical half-round groove 40 in which the aforementioned cross-bar 26 of the minor end of the coil is seated. It will be apparent, then, that when the bank of guns is in the loading position of FIG. 4a, each gun is adapted to receive over its muzzle sleeve 38 one inverted coil spring which may be positioned in one of two positions at the discretion of the operator, i.e., with the knots in one of two available positions displaced 180 from one another. It will further be apparent that if some orientation other than a trailing or leading position of the knots were desired, the same may be as well achieved by maintaining the same relative orientation of knot 28 and cross bar 26 as is illustrated in FIG. I, but changing the orientation of the grooved seat 40 in the muzzle sleeve 38 of the stapling gun. Such change would necessarily be limited to such rotative displacement of the grooved seat 40 as would continue to insure that the staple would straddle the cross bar 26.

in any event, the combination of the cross bar 26 at the bottom or small end of the spring coil and the diametrical seat 440 on the muzzle sleeve 38 of the gun serve to determine the rotative displacement or orientation of the coil, and to maintain that orientation while the coils rise from the loading position of FIG. 4a to the firing position of FIG. 4b.

The sequence of these several operations is indicated more or less diagrammatically in FIG. 2. In FIG. 2, the inverted slat frame 32 is shown positioned for the connection thereto of the second row of spring coils, a first row having previously been stapled to the end or leading cross slat 30 of the slat frame. As earlier indicated, the gun 35 in lowered position corresponding to that of FIG. 4a is loaded with a spring coil 20 which is then elevated by upward movement of the gun to the broken line position of FIG. 2 at which the bottom convolution and the cross bar 26 of the spring are pressed firmly into contact with the second cross slat 31 of the base frame, and the upper or opposite side of that cross slat is firmly bucked by a backing bar 42 which serves as an anvil on the cross beam 44 against which to drive the staple into the slat.

The firing of the stapling gun 35 is preferably done with force sufficient to impress or to indent the cross bar 26 at the bottom end of the spring into the surface of the cross slats of the frame, the impact of this force being sufficient also to cause a slight bending of the cross bar in a vertical plane (See FIG. 1). The legs 46 of the staples 48 are preferably chisel-shaped so as to be bent into a curved configuration upon entering the wood, thereby to prevent their unintentional dislodgement, and to anchor the springs 20 securely in place.

The stapling accomplished, the guns are withdrawn, leaving their spring coils secured to the frame.

As will be apparent from FIG. 2, as well as from FIGS. 3 and 4, the stapling is performed with the springs 20 and the slat frame 32 in an upside-down condition, thus to use the force of gravity to maintain the desired orientation of the individual coil springs with the muzzles 38 of the stapling guns.

ELEVATING AND FIRING THE STAPLING GUNS The stapling mechanism, illustrated to the far left of FIG. 3 as well as in FIGS. 40 and 4b and 5, is carried on a stationary frame, which comprises a pair of spaced standards 50 which are weldments of steel plate connected together at their upper ends by the cross beam 44, which is of inverted T section, and at their lower ends by cross bracing 52 of any suitable configuration. Above the lower cross brace, the standards are also joined by a tubular manifold 54, which is connected to a source of pressure air, and to which the individual stapling guns 35 areconnected by suitable flexible hoses 56, (FIG. 5) the manifold chamber having a volume sufficient to ensure that the guns will be powered uniforrnly.

The guns themselves are mounted upon the reciprocable carriage 36 which includes a pair of slide members 58, one at each end of the carriage, connected by a cross beam 60 upon which the stapling guns are firmly clamped at uniform height in bolted pillow blocks 62. Each slide member 58 is movable upon a vertical slide shaft 64 or way which is secured in brackets 65 affixed to the adjacent standard of the frame. Each slide 58 is provided on the side opposite the operators position with a rack 66 fixed thereon, and each rack is engaged with a pinion 68 secured to a cross shaft 70 extending between, and journaled in bearings in, the opposed standards 50 of the stationary frame. One end of the shaft 70, as seen in FIG. 3 and at the left hand side of FIG. 4a, is provided with a driven pinion 72 which is in turn engaged by a reciprocable rack 74 connected to the piston rod of a double-acting air cylinder 76, the rack 74 being backed on its side opposite its teeth by a roller 77 to take the side thrust of the toothed engagement.

As will be seen by comparing FIGS. 3, 4 and 5, the extension of the rack 74 by the driving cylinder 76 rotates the shaft 70, which, through the pair of gears 68 engaged with the racks 66 fixed to the slides 58 of the gun carriage, causes the guns 35 thereon to move upwardly to the position of FIG. 4b to carry the springs 20 into contact with the cross slats of the slat frame 32.

The guns are connected for unison firing by a common triggering bar 78 which is carried by and therefore moves with the gun carriage 36. The bar 78 is a square tube eccentrically mounted at its ends in bearings 79 on the slide members 58 so that when rocked, one of its corner edges engages the trigger 80 of each gun and causes the guns to tire in unison. The trigger bar is rotated by means of a double-acting air cylinder 81 mounted upon the carriage 36, and connected to a crank 82 on the trigger bar, causing the bar to rock when the piston of the firing cylinder is moved.

BUCKING THE SLAT FRAME WHILE STAPLING As may be appreciated from FIGS. 1 and 2, the inverted slat frame 32 is not of itself equipped to resist unyieldingly the impact of the staple because, when the guns are elevated to emplace the inverted coils against the downward face of the inverted slat, the thenupward surface of the slat would be out of contact with the upper cross beam 44, and would be supported firmly only under the longitudinal side rails 34 (and center rail when present) of the base frame. (See FIG. 4,7). It is, accordingly, desirable to transmit the firm support of the upper cross beam 44 directly to the cross slats in order to buck the same when the guns 35 are fired.

The backing bar 42 for bucking the cross slats, and the operating mechanism therefor, are best shown in FIGS. 4a and 4b, and in FIGS. 6a and 6c. The backing bars 42 are two in number, one on either side of the central feeding or indexing mechanism 83 by means of which the slat frame 32 is advanced through the apparatus. Each backing bar 42 is positioned in a slot 84 (FIG. 6a) in the flange of the inverted cross beam 44, and by means of lugs 86 is reciprocably mounted upon a pair of capped posts 88 each screwed into the upper side of the girder flange. The backing bars 42 are normally maintained in an upper or retracted position on the cross beam 44 by means of compression springs 90 which encircle the posts 88. When retracted, the lower edges of the bars 42 provide ample clearance for the passage therebeneath of the cross slats of the slat frame 32 as the same are being advanced by the indexing mechanism 83 with the ends of the cross slats 30 resting upon the angle-iron frame ways 92 seen in section in FIGS. 4a and 4 b, and in side elevation in FIG. 2 and in the several FIGS. 6.

To bring the backing bars 42 into supporting contact with the upper surface of a cross slat to resist the driving force of the staple, four cam levers 94, two for each backing bar, are ganged to a connecting rod 96 which in turn is pivotally connected to the clevis of the piston rod of a double-acting air cylinder 98 mounted at one end of the upper cross beam 44. As will quickly be seen from comparison of FIGS. 4a and 4b (also 6a and 6c), the extension of the piston rod of the cylinder causes the connecting rod 96 to move from left to right, as there seen, rotating the several cam levers 94 clockwise to cam the backing bars 42 downwardly into bucking contact with the cross slat of the frame.

The drive cylinder 98 for the backing bars 42 is connected to the operating valve that controls the drive cylinder 76 for elevating the gun carriage, so that pressure air is admitted to both simultaneously. However, inasmuch as the cylinder 98 is smaller in diameter as well as stroke, it completes its movement before the guns are fully elevated, assuring that the cross slat is solidly backed for the arrival of the guns and therefore solidly bucked for their firing.

Because the apparatus is adapted to be employed for the manufacture of box springs that vary in width, i.e., to accommodate at least the standard twin and doublebed widths, as well as others, the ways 92 upon which the slat frame 32 advances through the apparatus are adjustably mounted upon the flange of the cross beam 44, being suspended therefrom on brackets 100 that are adjustably clamped to the flange by means of set screws (FIG. 2). Similarly, to accommodate the narrower widths of the twin-size frame, the backing bar 42 is made adjustable in length by providing it with segmental engaging elements or shoes 102, which are attached to the reciprocable backing bar 42 by means of screws and which permit the convenient removal of a sizeable portion of the engaging edges of the bars to accommodate the twin size frame, or the complete replacement and substitution of different shoes in the event that other widths or slats arrangement of base frames is employed.

In a similar manner, the positions of the guns on the movable gun 36 can likewise be adjusted to control the intercoil spacing, as may be desired to accommodate other than the major sizes of box springs which will occupy the greater portion of the operating time of the apparatus.

FEEDING THE SLAT FRAME TO THE STAPLING STATION As is indicated generally in FIG. 3, a stack or magazine 103 of prefabricated slat frames 32 is supported upon a scissors elevator 104 which is operated on call by hydraulic power to elevate the stack of frames one frame thickness at a time to bring a new frame to the level of the frame ways 92 and into the operating range of the feed pawls of the indexing mechanism 83 after the preceding frame has advanced sufficiently to clear the leading edge of the stack. The stack elevator 104 is operated automatically by control means yet to be described.

The frame ways 92 extend from the magazine 103 to the stapling station, being supported at their rearward ends, adjacent the feed stack, by an upright frame comprising a pair of side columns 106 connected at their upper ends by upper cross beams 107 and 108, and a lower cross beam 109.

Upper cross beam 108 and lower cross beam 109 are connected by numerous vertical filler rails (not shown) which constitute an abutment against which to emplace the stack 103 of slat frames, whose side edges are guided by posts 110 on the frame elevator 104. They also support the control box 111.

The entering ends of the frame ways 92 are supported on a slide shaft 1 12 secured in brackets near the upper ends of the columns 106, the connections of each way to the shaft 112 being made by a bracket (not shown) that is secured to the way and adjustably locked in place on the slide shaft 112 by a set screw.

As shown in FIG. 3, the frame ways 92 extend forwardly to the front edge of the stapling mechanism support standards 50 from which point the inverted slat frame, after having received its coils, is transferred to extension ways (FIG. 8a only) from which to be re moved in any convenient manner for future operations.

The indexing mechanism 83 is the most complicated part of the apparatus and is shown in FIGS. 3, 4., the several FIGS. 6, and also in both FIGS. 8.

It consists essentially of double-acting double-ended air cylinder 114 whose reciprocable piston rod 116 is suitably extended and fitted with three depending feed dogs or pawls 118, 120 and 122, of which the pawl 118 is normally inoperative, being called into operation only once for each frame to eject the frame from the apparatus upon the completion of the stapling of a row of coils on the last cross slat 33 of the frame.

As illustrated in FIG. 3, the drive cylinder 114 is mounted on the back side of cross beam 44 of the stapling mechanism, i.e., on the exiting side of the stapling station. At the rearward end of the piston rod 116 of the drive cylinder 114 there is fitted a bracket 124 from which the intermediate feed pawl 120 is suspended, and which also serves as a coupling for an extension rod 126 at the extreme rearward end of which there is similarly mounted a corresponding bracket 128 from which the rearward feed pawl 122 is suspended. The extension rod 126 is supported in a slide bearing 107(a) in the upper cross beam 107.

At a suitable time in the operating cycle the valve controlling the operation of the drive cylinder 114 is energized by the automatic controller, causing the piston rod 116 to be extended to its retracted position shown in FIG. 3, and then almost immediately, as in a continuous operation, to move forwardly causing the intermediate feed pawl 120 to engage a cross slat of the slat frame then on the ways, and to move that cross slat forwardly to the stapling station. At the same time, the rearward feed pawl 122 either assists in that feeding action during the time when both pawls are operative upon a single frame, or at times causes the rearward feed pawl 122 to engage a cross slat of the next frame of the magazine 1133 to move it onto the frame ways 92.

The intermediate and rearward feed pawls 120 and 122 are simply bars pivoted on a horizontal axis in their respective mounting brackets, chamfered at their front edges to match the generally vertical rearward edges of the cross slats of the slat frame 32, and urged by gravity to the operative position at which they are stopped by the engagement of their rearward ends with an abutting surface of their mounting brackets. Thus, on the rearward stroke of the rod of the cylinder 114, the feed pawls 124D and 122 ride freely over the next rearward cross slat of the frame, falling into position poised for the next feed movement (See dotted line position FIG. 60).

That portion of the indexing mechanism which serves to position the cross slat accurately for the receipt of a row of coils is shown in detail in the several FIGS. 6. in FIG. 6a, the leading cross slat 30 of the frame, which is wider than all of the intermediate cross slats 31 of the frame, is positioned at the stapling station to receive its row of coils. The feed pawl 120, under the driving force of the air cylinder 114, has moved the leading edge of the slat frame firmly against a pair of positioning stops 1311, each adjustably secured to one of two rock shafts 132 journalled in hearings on the upper side of the flange of the cross beam 44. The rock shafts 132 are also shown in FHG. 7 which also illustrates the torsion springs 134 by means of which the rock shafts are normally biased to lift the stops 130 out of the frameengaging position (FIG. 6b). The rock shafts flank the indexing cylinder 114, and each is rocked by its own separate crank 136 engaged by the cam end of a push rod 138. The pair of push rods 138 flank the piston rod 116 of the cylinder 114, and extend through slide bearings in the web of the T-shaped cross girder 44 to bearing blocks 140 secured to sides of a central channel member 142 cantilevered rearwardly from the web of the cross girder 44. The push rods 138 are positioned so that their chamfered or cammed front ends are posed to contact the roller of the rock-shaft crank 136 when the feed mechanism is in the retracted position. On each push rod 138 there is pinned a push block 144 which is normally engaged with the front face of the bearing block 140, being urged into contact therewith by a compression spring 146 surrounding the push rod between the push block 144 and the web of the cross girder 44 (FIG. 6b). In that position, the cam end of the push rod is fully retracted and the rock shaft 132 rotated by the torsion springs to remove the stop 130 from the path of the slat frame 32.

To place the stop 130 in operative position, the push rods 138 are advanced to the position of FIGS. 6a and 6c, the cam ends of the rods turning the cranks 136 to rotate the stop 130 to its depending position at which to intercept the leading edge of the frame 32. The push rods 138 are advanced by cross pins 148 extending sidewardly from the bracket 124, which on the fully retracted stroke of the piston rod 116, is positioned well to the rear of the push blocks 144. The push blocks 144 are in sliding contact with the sides of the support channel 142 to prevent the turning of the rod 138 on its own axis while it reciprocates (Compare FIG. 4 and 6).

Thus on the return or working stroke of the piston 114 the advancing feed pawl bracket 124 thrusts the push rods 138 forwardly to move the reciprocable frame stops 130 from the position of FIG. 6b to the position of FIG. 6a, thus to form an abutment against which the feed pawl positions the leading cross slat of the base frame.

The frame stops are actuated on every feed stroke of the machine, but as it depends from the rock shaft only sufficiently to engage the upper layer 30a of only the leading cross slat, it is in fact inoperative and of no consequence during the indexing of subsequent cross slats 31 and 33 of the frame.

From FIG. 611 it will be apparent that the frame stop 130 is in the stop position only during the last portion of the feed stroke of the indexing mechanism inasmuch, as there is a considerable amount of loss motion of the feed pawl bracket 124 before the push blocks 144 are engaged by the cross pins 143 (See FIG. 6b). This loss motion permits the trailing slat 33 of the base frame (which is also of double thickness) to clear the stapling station before the frame stop 130 is again depressed to intercept the leading cross slat 30 of the succeeding frame.

For the second and all succeeding cross slats of an individual base frame, the upper frame stop 130, as earlier indicated, is ineffective, and a second frame stop 150 is therefore provided, insertable through a notch or slot 152 through the supporting flange of the frame ways 92 from the under side thereof at the appropriate time to intercept the forward edge of the second and all succeeding cross slats of the frame. Its operation is illustrated in each of FIGS. 6a, 6b and 60, which together show not only how the lower frame stop 150 serves its function, but also how it is selectively disabled for the passage of the leading cross slat 30 of the slat frame.

The iower frame stop 150 is shown in operative position in FIG. 6c engaged with the forward edge of the second cross slat 31 which is firmly seated against it by the intermediate feed pawi 120 of the indexing mechanism. The lower frame stop is essentially hook-shaped and pivotally mounted on the underside of the frame way 92 to be rocked by a crank 154 into and out of frame-engaging position under the influence of an air cylinder 1S6 mounted on a bracket 157 secured to the way 92. The stop-actuating cylinder 156 is singleacting, having a self-contained spring (not shown) which tends to extend the piston rod so as to retract or withdraw the lower frame stop from engaging position. The cylinder is operated by a solenoid valve under the influence of a normally open switch 158 which is mounted on the support channel 142 and positioned to be operated by a cam bar 160 on the upper surface of the mounting bracket 124 of the intermediate feed pawl 120. Under normal conditions, therefore, when the mounting bracket 124 for the intermediate feed pawl 120 has advanced sufficiently to cause its upper cam bar 160 to depress the plunger of the control switch 158 of the frame-stop actuating cylinder, the frame stop 150 rises into the frame ways to intercept the oncoming cross slat 31 of the base frame. Conversely, as the feed pawl 120 retracts for another indexing movement, the switch 158 is opened before the end of the retraction stroke (dotted line position FIG. 6c) and the lower frame stop 150 drops away to the position shown in FIG. 6b which it maintains until, on the subsequent feed stroke, the cam bar 160 again actuates the switch 158 to apply air to the cylinder 156 and to elevate the lower frame stop 150 into engaging position.

In order to disable the lower frame stop 150 for the positioning of the leading cross slat 30, which is too wide to be serviced by the lower stop, a second and normally closed switch 162 is mounted on the upper side of the flange of the cross girder 44 with its operator positioned to be intercepted by the upper portion 30a of the leading cross slat of the frame. That switch is in series with the normally open switch 1S8.*When that switch is operated as indicated in FIG. 6a, the switch 162 is opened, rendering it impossible to close the control circuit to the valve controlling the lower frame stop Therefore, as long as the switch 162 indicates the presence of the leading cross slat 30, the lower frame stops 150 remain inoperative, and the leading edge of the frame advances to the upper stop 130.

Again, since the trailing cross slat 33 is the mirror image of the leading slat 30, i.e., with the upper thickness thereof disposed at the right-hand side or trailing edge of the last cross slat, it is not in a position to actuate the switch 162 before the leading edge of the trailing slat contacts the lower stop 150, and therefore is of no effect in disabling the lower frame stop 150 for the interception of the last or trailing cross slat 33 of the frame.

ELEVATENG THE FRAME STACK AND SPACING THE FRAMES It will be apparent from FIG. 3 that as approximately one-half of a slat frame has advanced through the stapling station, the trailing edge of the frame will clear the supply stack 103.. While the uppermost frame is on the ways in transit to the stapling station, one of its longitudinal side rails is followed on its then upper surface by the depending operators of a pair of sensing switches 164 and 166 which are mounted on a bracket 168 secured to the frame way 92, and spaced longitudinally of the direction of travel of the slat frame through the apparatus, the rearward switch 166 being disposed above the leading edge of the stack of frames 103, and the forward switch 164 being positioned forwardly thereof above the frame ways.

Both the sensing switches 164 and 166 are of the normally closed type, and are wired in series with the elevator motor starter so that the closing of both is required to call the elevator into operation. Thus, when the slat frame in the frame ways in the stapling apparatus clears the forward switch 164, a circuit is finally completed through both switches, and the stack begins to rise until the rearward switch 166 is once more operated to open the circuit. The uppermost frame of the stack is then at the level of the frame ways 92, and on the next indexing movement opens the forward switch 164 as well.

It will be apparent from the foregoing that the spacing of the two sensing switches 164 and 166 controls the spacing between successive slat frames, which is set at a distance slightly in excess of the normal interslat spacing so as to allow for the greater width of the leading slats of the frame. As the increment of movement is the length of the feed stroke of the indexing mechanism, it will be apparent that the interframe spacing will be the length of the feed stroke or some multiple thereof, determined by the placement of the forward switch 164 along the frame way. One feed stroke is sufficient for the purpose, which is in part to permit the intermediate feed pawl to drop into position behind the last or trailing cross slat 33 of the frame so as to thrust it forwardly to the stapling station. It will be apparent at the same time that this necessary gap between successive frames establishes the need for one indexing movement that is not accompanied by the other steps of the normal operating cycle. For this purpose the electrical control mechanism is arranged for manual operation of each of the functions separately, so that the operator by actuating the necessary switch, can effect one independent indexing movement, advancing the leading slat of the succeeding frame into the stapling station.

It is similarly necessary to preserve the interframe spacing at the stapling station for the discharge of the completed frame and the arrival of the succeeding frame in order to provide clearance for the lowering of the upper frame stop 130, i.e., because of the necessity of inserting the stop after the completed frame clears the station, and before the succeeding frame arrives, it is not possible to utilize the succeeding frame to push the completed frame on its way. A separate ejector mechanism is therefore provided at the exiting end of the apparatus.

EJECTING THE COMPLETED ASSEMBLY The ejector pawl 118, as will be seen in FIG. 3, is a forward extension of the indexing mechanism 83. Together with its controller, it is shown in greater detail in FIG. 8, the pawl 118 also being seen in end view in FIG. 7.

Whereas the intermediate feed pawl 120 and the rear feed pawl 122 are urged by gravity to a depending operative position, always either engaged with or poised for engagement with a frame cross slat except during the retracting stroke, on which those slats are overriden, the forward ejector pawl 118 is normally inoperative, being lifted and maintained out of frame engaging position by a small single-acting air cylinder 170. The pawl itself is pivotally suspended from a bracket 172 affixed to the forward end of the piston rod 116, and by its unbalanced weight is urged to the broken line frame engaging position of FIG. 8a. It is also urged into that position by a return spring (not shown) which is within and part of the air cylinder 170 which is mounted on the forward face of the pawl bracket 172 and has attached to its downwardly extending piston rod a lifting arm 174 which is pivotally connected to the pawl 118 by a pin-and-slot connection 176 within a recess 1'78 milled in the pawl forwardly? of its main pivotal mounting. When the air cylinder 170 is energized, therefore, the ejector pawl 118 is lifted and maintained in its elevated position, where it remains idle throughout the normal operation of the indexing mechanism, air being constantly supplied to the cylinder 170 except when the last or trailing cross slat 33 of the frame is positioned at the stapling station (and fleetingly and ineffectively during the arrival of the leading cross slat 30 at the stapling station).

The control of the forward ejector pawl 118 is effected by a small air valve 180 through which pressure air is normally applied to the cylinder 170. The valve is mounted on a bracket 182 screwed to the flange of the cross beam 44 and positioned so that its operating leaf 134 will be lifted by the upper layer 33a of the trailing cross slat 33 when the latter is positioned at the stapling station. When the valve is operated by lifting the operating leaf 184 the connection to the pressure source is interrupted and the cylinder is vented to atmosphere through the valve body. Thus, when the operating leaf is lifted to the dotted line position shown in FIG. 8b, the feed pawl 118 is correspondingly depressed to the broken-line, slat-engaging position of FIG. 8a, and remains so poised for the indexing movement that completes the last stapling cycle for a given frame. On the retraction stroke, the pawl 118 overrides and falls behind one of the intermediate cross slats 31 of the completed frame, and on the forward stroke removes it from the stapling station.

Inasmuch as the upper layer 33a of the last cross slat 33 is in engaging contact with the valve-operating leaf 184 for a distance less than the length of the indexing stroke, pressure air is re-admitted to the air cylinder before the ejection stroke of the forward feed pawl 118 is completed. Thus, to maintain the engagement of the ejector pawl 118 with the frame, the former is provided ,with a forwardly extending lower lip 186 which maincompleted frames in the extension ways should not permit disengagement in that manner, it will occur at the beginning of the next retraction stroke of the indexing mechanism, the lifting force of the cylinder being inadequate to damage the mechanism.

Inasmuch as the valve 180 is operated by the passage thereunder of the upper layer 33a of the trailing slat 33, it will be apparent that it is similarly lifted by the upper layer 30a of the leading slat 30, but only momentarily as will be apparent from comparison of FIG. 6a, which illustrates the leading cross slat at the stapling station, with FIG. 8b, which shows the trailing cross slat similarly so positioned. Thus, the ejector pawl 118 is momentarily but idly positioned in the broken-line position of FIG. 8a as the intermediate feed pawl 120 moves the leading cross slat 30 into the stapling station.

ELECTRICALLY CONTROLLING THE CYCLIC OPERATION Central to the operation of the circuit is a motordriven industrial timer 111, the elements of which are enclosed within the broken line of FIG. 9. They include a timing shaft driven by a motor 191 which is placed into operation by an initiating manual switch 192 which is preferably a pedal-operated switch at the operators position in front of the stapling station, and a holding switch 194 operated by a cam on the motordriven shaft. The holding switch continues to apply power to the driving motor when the initiating manual switch 192 is released, holding the motor in for essentially one revolution of the shaft after which the holding switch 194 opens, de-energizes the motor, and thus determines the length of an operating cycle.

On the same shaft 190 are three other cam-operated switches 196, 197, and 198 controlling respectively the solenoid valves 200, 201, and 202 which control respectively the air cylinder 76 which elevates the gun carriage, and with it the air cylinder 98 which depresses the backing bars, the latter two being controlled in common by the valve 200, the air cylinder 81 which rocks the trigger bar to fire the guns, and the air cylinder 114 that powers the indexing mechanism 83. The cam-operated or timing switches 196, 197 and 198 are each connected to their respective controlled solenoid valves through one of three manually operated threepole switches 203, 204 and 205 the lower contacts of which must be closed to render the automatic controller operative. A fourth manually-operated three-pole switch 206 serves essentially to condition the slat frame magazine 103 for automatic operation.

It will be aparent from the diagram that the timing motor 191 is connected to power through the lower set of contacts of each of the aforementioned manually operated three-pole switches 203 to 206, inclusive, requiring that all such contacts be closed before the timing motor may be energized, and also that the circuit to the timing motor is interrupted if any of those contacts should be opened. A third set of contacts of each of the four triple-pole switches 203, 204 and 205 operate signal lamps 207, 208, 209 and 210 to indicate that the timer switches 196, 197 and 198, the elevator 104, and the timer motor 191 are conditioned for operation.

It will be apparent then that when the cycle-initiating switch 192 is manually closed by the operator after he has closed each of the aforementioned four triple-pole switches 203 to 206 inclusive, the timer shaft 190 commences to turn causing, successively, the guns 35 to elevate as the backing bar 42 comes down, the trigger bar 78 to rock and to fire the guns, the guns to retract, and the slat frame 32 to index in preparedness for the beginning of the next cycle. Each of the air cylinders 76, 98, 81 and 114 controlling these four basic movements is a double-acting cylinder and, accordingly, the solenoid valve which controls each is a two-position springreturn valve which normally applies pressure air to one side of the operating piston while venting the other, but reverses that condition when the controlling timer switches 196 to 198 are closed to power the valve solenoids.

The air cylinders 156 that operate the lower frame stops 150 are of the single acting type, as earlier mentioned, and spring-biased to retract the lower frame stops from their frame engaging positions (FIG. 6b). The valve 212 which controls the cylinder 156 is itself controlled by the earlier-mentioned normally closed switch 162 mounted on the upper surface of the cross beam 44. These two switches, as shown in FIG. 9, are connected in series and when closed cause the admission of pressure air to the cylinder 156 to elevate the lower frame stop. As earlier pointed out, the normally open 158 switch is closed after the indexing stroke has proceeded sufficiently to permit the preceding cross slat to clear the stapling station, so that the lower stop 150 may resume its position without obstruction.

The two normally closed switches 164 and 166, which energize the drive motor of the hydraulic lift mechanism 104 of the frame magazine 103, are connected in series to the drive motor through the same set of contacts of the switch 206 that light the signal lamp 210, the switch 206 thus interlocking the elevator 104 with the timer motor 191. As earlier explained, the removal of one slat frame from the top of the magazine 103 permits the switch 166 to close, and when the trailing edge of that frame has finally cleared the forward switch 164, the elevating motor is energized, lifting the stack 103 until its uppermost frame again opens the rearward switch 166. When the magazine is empty and the last frame has also cleared the forward switch 164 the elevator proceeds to its maximum height at which point, with the hydraulic ram fully extended, its pump bypasses until the operator shuts it off. This he does by manually operating the triple pole switch 206, the middle contactor of which is connected for double-throw operation, and applies power to a solenoid to open a valve 214 which vents the hydraulic lift cylinder to its sump permitting the elevator 104 to descend to be recharged with a new stack.

Each of the solenoid valves 200, 201 and 202 may likewise be operated individually by manual switches 216, 217, and 218 respectively, for testing and maintenance.

The entire control circuit is connected to power through a doubie-pole single throw switch 219, both lines to which are appropriately fused in accordance with conventional practice.

CONCLUSlON in the foregoing description, I have set forth what i believe to be a full disclosure of a new apparatus of fabricating box spring assemblies by the stapling technique made possible in part by modification of the spring coil for assembly to the slat frame by a gun inserted axially through the interior of the spring. With this spring and by this gun it is possible to secure the cone coil to the box spring frame by means ofa single staple and, if adequate force be used in driving the staple, the spring can be locked against rotational dislodgement by having its stapled part impressed into the surface of the wood. This single staple connection is sufficient, after the top face of the spring assembly is united by whatever interlacing or joining technique may be chosen, to maintain securely the connection of the smaller bottom end of the spring coil to the wooden slat frame.

In the apparatus l have found it advantageous to employ the weight of the individual coils as the method of maintaining their orientation with the stapling gun and thus to perform the stapling with the stapling guns pointed upwardly, and with the springs and the slat frames upside down. The indexing mechanism by means of which the slat frame is fed to the stapling apparatus one slat at a time is such as to square" the slat at the stapling station to assure that the springs are attached in a line parallel to the slat edges, and, in the case of the intermediate slats, centrally thereof. This is accomplished, notwithstanding any slightly skewed positioning of an individual cross slat, by feeding the frame with a feed pawl that engages the slat at or near the center of its trailing edge while positioning the slat with two widely spaced abutments or stops that engage the leading edge of the slat near its ends, and utilizing sufficient feeding force to assure tight ultimate contact of the slat with all three.

The features of my improved coil and apparatus believed patentable are set forth in the appended claims.

What is claimed is:

1. A stapling gun for stapling helical wire coil springs to a base frame in the manufacture of box springs or the like having a muzzle portion long enough for insertion through the spring axially thereof, a sleeve surrounding said muzzle and conforming with sliding clearance to the interior shape of the spring, said sleeve having a conical nose portion to facilitate its entry into the spring and a groove in its end face to position a wire to be straddled by a staple fired by the gun.

2. The gun of claim 1 in which at least the outer surfaces of the muzzle sleeve are of a slippery material such as Teflon plastic.

3. Apparatus for stapling wire springs in rows to base frames in the manufacture of box springs or the like, comprising a stationary frame,

a carriage and a row of upwardly pointed stapling guns thereon,

said carriage being movable on said frame to elevate said guns from a lower loading position, at which each gun is poised to receive a spring, to an upper firing position, at which each spring is carried by its gun against the underside of an inverted base frame and stapled thereto,

backing means engageable with the base frame on its top side in opposition to the guns to buck the same when fired,

frame ways upon which to support the base frame for movement to the stapling station, and

indexing means for advancing said base frame incrementally for the stapling thereto of successive rows of springs.

4. The apparatus of claim 3 in which the frame ways are adjustably spaced to support frames of varying width.-

5. The apparatus of claim 3 in which the indexing mechanism is especially adapted for base frames comprising a plurality of cross slats connected together in spaced relation, and in which the frame is indexed slatby-slat for the stapling of a row of coils to each slat, said indexing means comprising a reciprocable feed pawl freely movable over said slats in the retracting direction but abuttable therewith centrally of the slat on its trailing edge when moved in the advancing direction, and two widely spaced stops engageable with the leading edge of the slat near the ends thereof, said pawl and stops serving to square the slat into alignment with the row of guns on the carriage.

6. The apparatus of claim in which the indexing mechanism is extended rearwardly and provided with an auxiliary feed pawl operable in unison with said first mentioned feed pawl, an elevator mechanism adapted to support a stack of slat frames and to elevate the same to place the uppermost frame of the stack at the level of the frame ways and in the effective working zone of said auxiliary feed pawl, a pair of sensing switches operated in sequence by said uppermost frame upon reaching said level and subsequently upon advancing along the ways during a subsequent feed stroke of said auxiliary feed pawl, said elevator mechanism being operative to elevate the stack whenever an advancing slat frame clears both switches, the spacing between successive slat frames being controlled by the spacing of said switches.

7. The apparatus of claim 3 especially adapted for a base frame comprising a plurality of slats attached to longitudinal side rails and in which the backing means includes a beam overlying the slat frame at the stapling station and having thereon a reciprocable backing bar movable into contact with the underlying frame slat in alignment with said guns in firing position, thereby to absorb the impact of the firing of the guns. 

1. A stapling gun for stapling helical wire coil springs to a base frame in the manufacture of box springs or the like having a muzzle portion long enough for insertion through the spring axially thereof, a sleeve surrounding said muzzle and conforming with sliding clearance to the interior shape of the spring, said sleeve having a conical nose portion to facilitate its entry into the spring and a groove in its end face to position a wire to be straddled by a staple fired by the gun.
 2. The gun of claim 1 in which at least the outer surfaces of the muzzle sleeve are of a slippery material such as Teflon plastic.
 3. Apparatus for stapling wire springs in rows to base frames in the manufacture of box springs or the like, comprising a stationary frame, a carriage and a row of upwardly pointed stapling guns thereon, said carriage being movable on said frame to elevate said guns from a lower loading position, at which each gun is poised to receive a spring, to an upper firing position, at which each spring is carried by its gun against the underside of an inverted base frame and stapled thereto, backing means engageable with the base frame on its top side in opposition to the guns to buck the same when fired, frame ways upon which to support the bAse frame for movement to the stapling station, and indexing means for advancing said base frame incrementally for the stapling thereto of successive rows of springs.
 4. The apparatus of claim 3 in which the frame ways are adjustably spaced to support frames of varying width.
 5. The apparatus of claim 3 in which the indexing mechanism is especially adapted for base frames comprising a plurality of cross slats connected together in spaced relation, and in which the frame is indexed slat-by-slat for the stapling of a row of coils to each slat, said indexing means comprising a reciprocable feed pawl freely movable over said slats in the retracting direction but abuttable therewith centrally of the slat on its trailing edge when moved in the advancing direction, and two widely spaced stops engageable with the leading edge of the slat near the ends thereof, said pawl and stops serving to square the slat into alignment with the row of guns on the carriage.
 6. The apparatus of claim 5 in which the indexing mechanism is extended rearwardly and provided with an auxiliary feed pawl operable in unison with said first mentioned feed pawl, an elevator mechanism adapted to support a stack of slat frames and to elevate the same to place the uppermost frame of the stack at the level of the frame ways and in the effective working zone of said auxiliary feed pawl, a pair of sensing switches operated in sequence by said uppermost frame upon reaching said level and subsequently upon advancing along the ways during a subsequent feed stroke of said auxiliary feed pawl, said elevator mechanism being operative to elevate the stack whenever an advancing slat frame clears both switches, the spacing between successive slat frames being controlled by the spacing of said switches.
 7. The apparatus of claim 3 especially adapted for a base frame comprising a plurality of slats attached to longitudinal side rails and in which the backing means includes a beam overlying the slat frame at the stapling station and having thereon a reciprocable backing bar movable into contact with the underlying frame slat in alignment with said guns in firing position, thereby to absorb the impact of the firing of the guns. 